defineModel ref not reactive

[ant32t]

Is this expected that model is not reactive in the following example? When changing it to <Comp :model-value="reactive([])"/> it works. Is this a bug?

App.vue

<script setup>
import {reactive} from 'vue'
import Comp from './Comp.vue'
</script>

<template>
  <Comp :model-value="[]"/>
</template>

Comp.vue

<script setup>
import { watchEffect, ref } from 'vue';

const model = defineModel();
const msg = ref(0);
watchEffect(() => msg.value = model.value.length);
model.value.push(5);
</script>

<template>
    lenght of model:  {{ msg }}
</template>

[LinusBorg]

The ref is reactive, but not deep-reactive. And the prop value you provided is a plain, nonreactive array.

It works like a normal prop in that regard - if you pass something non-reactive down through a prop, changes will not trigger anything.

Changing the array will not trigger anything, as you did not rlassign a new value to the model ref